1. Field of the Invention
The present invention relates to a vehicle seat with suspension device, and in particular to a belt anchor mechanism for connection with a seat belt adapted to hold and restrain an occupant on the seat.
2. Description of the Prior Art
In some of vehicles, especially automobiles, a suspension device is provided between the seat and floor for the purpose of resiliently supporting the seat to absorb a vibration or shock caused in running on a bad road and so forth.
In most instances, a suspension device of this kind is of such a typical structure that X-shaped links are provided between an upper frame fixed on the bottom of a seat and lower frame fixed on the side of vehicle floor so that the upper frame is vertically movable via the X-shaped links relative to the lower frame, and a spring is extended between the X-shaped links and those frames, with a shock absorber being interposed between the upper and lower frames, whereby with this structure, suspension action is performed by virtue of the spring and shock absorber.
The seat provided with such suspension device has been with a problem as to a seat belt anchor thereon, in that the structure of the belt anchor involves a high possibility, when a great impact is applied, of causing a damage to the suspension device and of pulling the seat belt so strongly as to give an excessive pressure to an occupant on the seat. In other words, for example, in the case of the belt anchor fixed on the seat or the upper frame of the suspension device, when a collision accident occurs, a reaction force exerted by the occupant is directly transmitted to the suspension device, resulting in the breakage of the suspension device which may be a critical cause that the occupant will be thrown out. On the other hand, in the case of the belt anchor fixed on the side of vehicle floor, the vertical movement of the suspension device, even in driving on a normal road, causes undesired excessive fastening of the seat belt around the occupant.
In an attempt to solve the foregoing problem, there has been proposed a dual belt anchor structure consisting of a first belt anchor fixed on the seat or the upper frame of suspension device and a second belt anchor fixed on the side of vehicle floor, wherein the first belt anchor is connected with the second belt anchor via a second belt or link, so that, in a collision accident, a reaction force exerted by the occupant to the seat belt is transmitted and escaped to the vehicle floor.
However, the above-mentioned dual belt anchor structure employed in conventional seat with suspension device is found disadvantageous in its complexity due to the fact that the two belt anchors as well as the second belt or link are required for installation of a seat belt on the seat, and further has a shortcoming in that the second belt needs to be adjusted its length so as to be loosened, considering the stroke amount of vertical movement of the suspension device as well as the movement range of slide rails, and the degree of loosening of the second belt varies depending on different forward/backward positions of the seat adjusted by the occupant, which makes the occupant feel uneasy about the unstable state of seat belt and hard to trust the seat belt in sitting on the seat.